Stabilized acrylonitrile polymer composition and method of making same



Unite States atent STABILIZED ACRYLONITRILE POLYMER COMPO- SITION AND METHDD OF MAKING SAME Hobson D. De Witt and Patrick H. Hobson, Decatur, Ala., assignors to The 'Chemstrand Corporation, De= catur, Ala a corporation of Delaware No Drawing. Filed-May 23, 1956, Ser. No. 586,685

16 Claims. (Cl. 260--29.6)

This invention relates to the stabilization of acrylonitrile polymers and blends thereof. More particularly, it relates to the stabilization of acrylonitrile polymers and blends thereof which have a tendency to develop color upon standing or application of. heat.

The term tpolymer, as employed in the instant de-. scription and claims, is intended to include homopolymers, eopolymers, blends thereof, and graft polymers, said polymers, containing at least 80 percent by Weight of polymerized or copolymerized acrylonitrile in the polymer molecule.

Acrylonitrile, polymers containing 80 percent or more of acrylonitrile are generally insoluble in the more common solvents. And, in those instances where suitable solvents have been found, in order to effect solution, the application of heat is usually necessary. Where heat is employed to effect solutions, from which shaped articles are to be formed, a. tan to dark brown color frequently develops. in the solutions andtherefore is. carried'over into the product formed therefrom. This color also develops in solutions upon standing for prolonged periods of time.

The mechanism which causes color formation has not been definitely ascertained, although a variety of reasons therefor have been. advanced. The presence. of metal ions, suchas iron, copper and manganese in the solutions may cause. the. color. The employment of amide compounds as. solvents may result in; formation of amines when, heat is applied and cause color in the compositions. Impurities present in. the solvents. have also been cited as a cause. Whatever may be the reason for color formation, it results in compositions and products; of undesirable s a r nd heref re. ha been the so rce of onc rn, particularly in commercial operations where. such types of. P y r o p yme s are emp oyed.

Accordingly, it is an object of the present invention to prevent undesirable color formation in acrylonitrile polymer compositions.

Another object is to minimize color formation when solutions of the acrylonitrile polymers are. permitted to stand for a prolonged period of time or upon application of heat. 7

It is also an object of the invention to prevent color formation in acrylonitrile polymers at elevated temperatures.

A still further object of theinvention is the production of solutions of acrylonitrile polymers and articles pro-' duced therefrom having improved: color characteristics.

Other objects and advantages will be apparent from a consideration of the description .of the invention which follows hereafter.

In general, the objects of the invention are accomp s y ss lvin h po ymer f cry oni r l in a. suitable solvent therefor and preventing or minimizing color formation by the presence in the solution as an inhibiting agent, a combined reagent comprising. an, aldehyde and an inorganic acidhaving an ionization. constant assent being present in a range. of from 99 to 1 percent in atwo component system. The total: amount of inhibiting agent may be employed in. a range of about .01 to 2.0 percent based on the total weight of the polymer solution which is the preferred range. The inhibiting agent.

may be added to the solvents before or after the polymer is dissolved therein. The inhibiting agent permits. exposure to high temperatures for. prolonged standing periods Without; the; developmentv of the objectionable. color which usually results in such solutions. The com-. positions of the instant invention may be prepared in a varying temperature range. For example, the. compositions of the instant invention may be prepared by mixing the polymer, a suitable solvent and the inhibiting agent at any temperature or heating the. mixture to a tempera. ture up to the boiling point of the solvent.

Among the solvents which may be used in practising the instant invention are. N,N-dimethylf.ormamide, N,N- dimethylacetamide, aqueous. zinc chloride, sulfuric. acid, aqueous nitric acid, aqueous sodium thiocyanate, ethylene carbonate, sulfolane, nitromethaneetc.

The, polymeric materials, which may be employed in the practice. of the. present invention, are polyacrylonitrile, copolymers, including binary and ternary polymers containing. at least. percent by Weight ofacrylem'trile in the polymer moleeule,'or a blend comprising'polyacrylonitrile or copolymers comprising acrylonitrilewith from 2 to 50 percent ofanother polymeric material, the'blend having an overall polymerized acrylonitrile content of at least 80 percent by weight. While the preferred polymers for use in the instant invention arev those containing at. least, 80 percent of acrylonitrile, generally recognized as the fiber-forming acrylonitrile polymers, it will be understood that the invention is likewise applicable to polymers containing less than 80 percent acrylonitrile and the same stability is realized with the inhibiting agents defined herein. The acrylonitrile polymers containing less than 80 percent. acrylonitrile are useful in forming'films, coating compositions, molding operations, lacquers, etc., in all of which applications the alleviation of undesirable color is extremely important.

For example, the polymer may be a copolymer of from 8Q to 9.8. percent acrylonitrile'and from 2 to 20 percent. of another monomer containing the C=C. linkage and copolymerizable with acrylonitrile. Suitable monoolefinic monomers include acrylic, alpha chloroacrylic andmethacrylic acids; the. acrylates, such as methylmethacrylate, ethylmethacrylate, butylmethacrylate, methoxymethyl methacrylate, beta-chloroethyl 'methacrylate, and the corresponding esters of. acrylic and alpha-chloroacrylie acids; vinyl chloride, vinylfluoride, vinyl bromide, vinylidene chloride, .l-chloro=lbromoethylene; m'ethacrylonitrile; acrylamide and methacrylamide; alphachloroacrylamide, 0r. monoalkyl substitution products thereof; methyl vinyl ketone; vinyl carboxylates, such as vinyl acetate, vinyl. chloroacetate, vinyl propionate, and vinyl stearate; N-vinylimidessuch. as N-vinylphthalimide and. N-vinyIsuccinimide; methylene malonic esters; itaconic acid. and itaconic ester; N-vinylcarbazole; vinyl furane; alkyl vinylesters; vinyl sulfonic' acid; ethylene alpha, beta-dicarboxylic acids or their anhydrides 'or derivatives,

. such as diethylcitraconate, diethylmesaconate, styrene;

vinyl naphthalene; vinyl-substituted tertiary heterocyclic Patente y 2 0 amines, such as the vinylpyridines and alkyl-substituted vinylpyridines, for example, 2-vinylpyridine, 4-vinylpyridine, Z-methyl-S-vinylpyridine, etc.; l-vinylimidazole and alkyl-substituted l-vinylimidazoles, such as 2-, 4-, or 5- methyl-l-vinylimidazole, and other C=C containing polymerizable materials.

The polymer may be a ternary interpolymer, for example, products obtained by the interpolymerization of acrylonitrile and two or more of any of the monomers, other than acrylonitrile, enumerated above. More specifically, and preferably, the ternary polymer comprises acrylonitrile, methacrylonitrile, and 2-vinylpyridine. The ternary polymers preferably contain from 80 to 97 percent of acrylonitrile, from 1 to 20 percent of a vinylpyridine or a l-vinylimidazole, and from 1 to 18 percent of another substance, such as methacrylonitrile or vinyl chloride. Y

The polymer may also be a blend of polyacrylonitrile or of a binary interpolymer of from 80 to 99 percent acrylonitrile and from 1 to 20 percent of at least one other C=C containing substance with from 2 to 20 percent of the weight of the blend'of a copolymer of from to 70 percent of acrylonitrile and from 30 to 90 percent of at least one other C=C containing polymerizable monomer. Preferably, when the polymeric material comprises a blend, it will be a blend of a copolymer of 90 to 98 percent acrylonitrile and from 2 to 10 percent of another mono-olefinic monomer, such as vinyl acetate, which is not receptive to dyestuff, with a sufiicient amount of a copolymer of from 10 to 70 percent of acrylonitrile and from 30 to 90 percent of a vinyl-substituted tertiary heterocyclic amine, such as vinyl pyridine or l-vinyl-imidazole, to give a dyeable blend having an overall vinyl-substituted tertiary heterocyclic amine content of from 2 to 10 percent, based on the weight of the blend.

The polymer may also be a graft polymer provided by polymerizing acrylonitrile in the presence of a preformed polymer, such as polymethyl vinylpyridine, and in which the polymethyl vinylpyridine is present in the range of 1 to 20 percent in the graft polymer.

The polymers, useful in the practice of the present invention, may be prepared by any conventional polymerization procedure, such as mass polymerization methods, solution polymerization methods, or aqueous emulsion procedures. However, the preferred practice utilizes suspension polymerization wherein the polymer is prepared in finely divided form for immediate use in the fiber fabrication operations. The preferred suspension polymerization may utilize batch procedures, wherein monomers are charged with an aqueous medium containing the necessary catalyst and dispersing agents. A more desirable method involves the semi-continuous procedure in which the polymerization reactor containing the aqueous medium is charged with the desired monomers and the continuous withdrawal of polymer may also be employed.

The polymerization is catalyzed by means of any water- I soluble peroxy compound, for example the potassium, ammonium and other water-soluble salts of peroxy acids, sodium peroxide, hydrogen peroxide, sodium perborate, the sodium salts of other peroxy acids, and any other water-soluble compound containing a peroxy group (.O-O-). A wide variation in the quantity of peroxy compound is possible. For example, from 0.1 to 3.0 percent by weight of the polymerizable monomer may be used. The catalyst may be charged at the outset of the reaction, or it may be added continuously or in increments throughout the reaction for the purpose of maintaining a more uniform concentration of catalyst in the reaction mass. The latter method is preferred because it tends to make the resultant polymer more uniform in its chemical and physical properties.

Although the uniform distribution of the reactants prepared by the saponification of animal and vegetable oils, the amino soaps, such as salts of triethanolamine and dodecylmethylamine, salts of rosin acids and mixtures thereof, the water-soluble salts of half esters of sulfuric acid and long chain aliphatic alcohols, sulfo- A nated hydrocarbons, such'as alkyl aryl sulfonates, and

any other of a Wide variety of wetting agents, which are in general organic compounds containing both hydrophobic and hydrophilic radicals. The quantity of emulsifying agents will depend upon the particular agents selected, the ratio of monomer to be used, and the conditions of polymerization. In general, however, from 0.01 to 1.0 percent by weight of the monomers may be employed.

The emulsion polymerizations are preferably conducted in glass or glass-lined vessels which are provided with a means for agitating the contents. Generally rotary stirring devices are the most effective means of insu'r ing the intimate contact of the reagents, but other methods may be successfully employed, for example by rocking or tumbling the reactors. The polymerization equipment generally used is conventional in the art and the adaptation of a particular type of apparatus to the reaction contemplated is within the province of one skilled in the art. The articles manufactured therefrom may be produced by well-known conventional methods, for example, the wet-spinning, dry-spinning and melt-spinning methods for producing fibers.

The following examples are illustrative rather than limitative and all parts, proportions and percentages are by weight unless otherwise specified.

EXAMPLE I 7.5 grams of polymeric acrylonitrile were added to 45 milliliters of N,N-'dimethylacetamide containing approximately 0.08 gram of titanium dioxide. The mixture was stirred and heated for 50 minutes at C. It was then quickly cooled to room temperature and the color measured. This sample was used as a control. The purity is recorded in Table I. The above procedure was repeated using 0.08 gram of sulfuric acid. Subsequently, a similar sample was prepared using only 0.08 gram of formaldehyde. The purity is set forth in Table I. The above procedure Was again repeated with 0.08 gram (1 percent) of sulfuric acid and 0.08 gram (1 percent) of formaldehyde added to the solvent. The data 7.5 grams of a polymer containing 94 percent acryloe nitrile and 6 percent of vinyl acetate were added to 45 milliliters of N,N-dimethylaceta.mide containing approximately 0.08 gram of titanium dioxide. The mixture was stirred and heated for 50 minutes at 90 C. It was then quickly cooled to room temperature and the color measured. This sample was used as a control. The purity is recorded in Table II. a The above procedure was repeated using only 0.08 gram of-sulfuric acid. Subsesquently', a similar sample was preparedi'using only 0.08 gram of formaldehyde. The purity i's set forth, in Table II} The procedure was again repeated with 0.08 gram;

(1 percent) of sulfuric acid and 010.8 gram (1; percent) of formaldehyde added. to the solvent, Subsequently, a series of samples containing various. percentages. of difi erent acids and aldehydes were. prepared by the same. procedure and the data recorded in Table. II below.

Table II Percent Acid Percent Aldehyde Purity 1,'% Sulfuric Acid EXAMPLE III 7.5 grams of a polymer blend of 88 percent of a copolymer containing 94 percent of acrylonitrile and 6 percent of vinyl acetate and 12 percent of a copolymer of 50 percent acrylonitrile-and SO-percent of 2i-methyl S-vi'nyh pyridine were added to 45 milliliters off -N, N-di methylacetamide containing approximately 0.08 gram of titanium dioxide. The mixture was stirred and heated for 50 minutes at 90 C. It was then quickly cooled to room temperature and the color measured. This sample was used as a control. The above procedure was repeated using only 0.08 gram of sulfuric acid. Subsequently, a similar sample was prepared using only 0.08 gram of formaldehyde. The purity is set forth in Table III. The procedure was again repeated with 0.08 gram (1 percent) of sulfuric acid and 0.08 gram (1 percent) of formaldehyde added to the solvent. Subsequently, a series of samples containing various percentages of different acids and aldehydes were prepared in the same manner and the data are set forth in Table III.

The data in the above examples show conclusively that a combined color inhibiting agent will produce unexpected results and that the constituents in the agent may be varied from an amount of acid in a range of about 50 to about 89 percent and from an amount of aldehyde in a range of about 11 to about 50 percent, based on the total weight of the inhibiting agent.

The tests for color indicative of approaching whiteness used throughout the examples consist of measurements of purity as calculated from the tristimulus 'values determined on a General Electric Spectrophotometer by the methods recommended by the Standard Observer and Coordinate System of the International Commission on Illumination, as fully set forth in the Handbook of Colorimetry published by The Technology Press, Massachusetts Institute of Technology, in 1936. Purity may be computed from chromaticity coordinates. Purity is a ratio of the amount of the spectrum component in this mixture to the sum of the spectrum and the daylight components.

The compositions of the instant invention present many advantages. For example, products formed from the polymer solutions of the instant invention are free of objectionable color and therefore of greater commercial yalue. In preparing the polymer solutions, heat may e applied. Wit o t h dense! Qf o orformation and e S lu ion i e ss ry, may ta d for pro g d peri sa remain re o ol r-. The inh bi in g n are readily available and inexpensive. Therefore, no great increase in productionv cost is necessary. The comp s t n co n g t nhibi o s may e. prepared without going through detailed and elaborate procedures that necessitate expensive changes in the design of the apparatus used. to manufacture. them.

It will be e stood o. ose s lled in. h art h t, many pp n y widely if re t em odiments f t is invention can bev made withoutdeparting from the spirit and scope thereof. Accordingly, it is to. be understood that i inv n ion. i not be limi e t the specifi embodiments thereof except as defined, in the appended claims.

Weclaim: a r r A1 e p i on of mattcr mnri ina a polymer selected. from. the group consisting of (:1) polyacrylonitrile, (2) a copolymer of at least 8.0 percent acrylonitrile and up to 20 percent of. another mono-olefinic monomer copolymerizable therewith. and (3 a polymer blend of to 99 percent of (A); a, copolymer of to 98' percent acrylonitrile and 2, to. 10 percent vinyl. acetate,

and 1 tov 2.0 percent of (B). a: copolymer of 10 to 70,

percent acrylonitrile and 30 to 90 percent of a tertiary heterocyclic amine containing a vinyl group attached directly to the heterocyclic nucleus, said blend having an overall tertiary heterocyclic amine content of from 2 to 10 percent based on the total weight of the blend, dissolved in a solvent therefor, and 0.01 to 2.0 percent,

employed in a range of about 11 to about 50 percent,

based on the total weight of said inhibiting agent.

2. A new composition of matter as defined in claim 1 wherein the acid is sulfuric acid and the aldehyde is formaldehyde.

3. A new composition of matter as defined in claim 1 wherein the acid is hydrochloric acid and the aldehyde is formaldehyde.

4. A new composition of matter as defined in claim 1 wherein the acid is phosphoric acid and the aldehyde is formaldehyde.

5. A new composition of matter as defined in claim 1 wherein the acid is sulfuric acid and the aldehyde is acrolein.

6. A new composition of matter as defined in claim 1 wherein the acid is sulfuric acid andv the aldehyde is propionaldehyde.

7. A new composition of matter as defined in claim 1 wherein the polymer is polyacrylonitrile.

8. A new composition of matter as defined in claim 1 wherein the polymer is a copolymer of 80 to 98 percent acrylonitrile and 2 to 20 percent of another mono-olefinic monomer copolymerizable therewith.

9. A new composition of matter as defined in claim 1 wherein the polymer is a copolymer of 80 to 98 percent acrylonitrile and 2 to 20 percent vinyl acetate.

10. A new composition of matter as defined in claim 1 wherein the polymer is a blend of 80 to 99 percent of (A) a copolymer of 90 to 98 percent acrylonitrile and 2 to 10 percent vinyl acetate and 1 to 20 percent of (B) a copolymer of 10 to 70 percent acrylonitrile and 30 to 90 percent Z-methyl-S-vinylpyridine.

11. A method for preparing a new composition of matter comprising mixing a polymer selected from the group consisting of (1) polyacrylonitrile, (2) a copolymer of at least 80 percent acrylonitrile and up to 20 percent of another mono-olefinic monomer copolymerizable therewith and (3) a polymer blend containing 80 to 99 percent of (A) a copolymer of 90 to 98 percent acrylonitrile and-21o 10 percent of another monorolefinic 0.01 to 2.0 percent based on the total weight of the.

polymer solution, of an inhibiting'agent containing an inorganic acid having an, ionization constant greater than 1.86 10'- and an aldehyde selected from the group consisting of formaldehyde, acetaldehyde, propionalde,

hyde, acrolein and benzaldehyde, said acid being employed in a range of about 50 to about 89 percent, and said aldehyde being employed in a range of about 11 to about 50 percent, based on the total weight of said inhibiting agent, and heating the mixture to a temperature in a range of 25 C. to the boiling point of the mixture to form a homogeneous solution.

12. The method as defined in claim 11 wherein the polymer is polyacrylonitrile. 1

13. The method as defined in claim 11 wherein the polymer is a copolymer of at least 80 percent acrylonitrile and up to 20 percent of another mono-olefinic monomer copolymerizable therewith.

, 14. The method as defined in claim 11 wherein the polymer is a copolymer of to 98 percent acrylonitrile and 2 to 20 percent vinyl acetate. v 1 1 15. The method as defined in claim 11 wherein the polymer is a polymer blend containing 80 to,99 P rcent of (A) a copolymer of to 98 percent acrylonitrile and 2 to 10 percent vinyl acetate and lto 20 percent of (B) a copolymer of 10 to percent acrylonitrile and 30 to 90 percent of a tertiary heterocyclic amine containing a vinyl group attached directly to the heterocyclic nucleus, said blend having an overall tertiary heterocyclic.

amine content of from 2 to 10 percent based on the total weight of the blend. 7

16. The method as defined in claim 15 wherein the tertiary heterocyclic amine containing a vinyl group attached directly to the heterocyclic nucleus is Z-methyl-S- vinylpyridine. i

References Cited in the file of this patent UNITED STATES PATENTS Mosse Oct. 30, 1956 

1. A NEW COMPOSITION OF MATTER COMPRISING A POLYMER SELECTED FROM THE GROUP CONSISTING OF (1) POLYACRYLONITRILE, (2) A COPOLYMER OF AT LEAST 80 PERCENT ACRYLONITRILE AND UP TO 20 PERCENT OF ANOTHER MONO-OLEFINIC MONOMER COPOLYMERIZABLE THEREWITH, AND (3) A POLYMER BLEND OF 80 TO 99 PERCENT OF (A) A COPOLYMER OF 90 TO 98 PERCENT ACRYLONITRILE AND 2 TO 10 PERCENT VINYL ACETATE, AND 1 TO 20 PERCENT OF (B) A COPOLYMER OF 10 TO 70 PERCENT ACRYLONITRILE AND 30 TO 90 PERCENT OF A TERTIARY HETEROCYCLIC AMINE CONTAINING A VINYL GROUP ATTACHED DIRECTLY TO THE HETEROCYCLIC NUCLEUS, SAID BLEND HAVING AN OVERAL TERTIARY HETEROCYCLIC AMINE CONTENT OF FROM 2 TO 10 PERCENT BASED ON THE TOTAL WEIGHT OF THE BLEND, DISSOLVED IN A SOLVENT THEREFOR, AND 0.01 TO 2.0 PERCENT, BASED ON THE TOTAL WEIGHT OF THE POLYMER SOLUTION, OF AND INHIBITING AGENT CONTAINING AN INORGANIC ACID HAVING AN IONIZATION CONSTANT GREATER THAN 1.86X10**5, AND AN ALDEHYDE SELECTED FROM THE GROUP CONSISTING OF FORMALDEHYDE, ACETALDEHYDE, ACROLEIN, PROPIONALDEHYDE, AND BENZALDEHYDE, SAID ACID BEING EMPLOYED IN A RANGE OF ABOUT 50 TO 89 PERCENT AND SAID ALDEHYDE BEING EMPLOYED IN A RANGE OF ABOUT 11 TO ABOUT 50 PERCENT, BASED ON THE TOTAL WEIGHT OF SAID INHIBITING AGENT. 